The present invention is related to the field of shock and vibration attenuation for media drives.
High performance disk drives are finely tuned electro-mechanical devices. The precision necessary to allow these devices to work is proportional to their capacity to hold customer data and their ability to handle the data in volume. Disk drive performance is dependent on the vendor""s drive design that includes the servo algorithms, spindle and disk pack balancing, internal damping and dynamic characteristics. Disk drive performance is also influenced by the environment in which it must operate.
In a quest for ever-shrinking cost per megabyte of storage, the track density, or tracks per inch (TPI) have increased. The TPI trend, along with efforts to reduce packing costs and unit footprints, has led to significant challenges regarding disk drive implementation. Obstacles presented to the industry consist of damping and attenuating the disk drive""s own internally generated vibrations, isolating the disk drive from vibrations created by neighboring disk drives, and isolating the disk drive from externally generated shocks and vibrations.
A poorly implemented disk drive mounting solution may cause various problems at a higher system level. An unconstrained, vibrating disk drive will tend to knock itself off track while performing a read or write seek. If the drive cannot successfully find the correct location to read or write on the disk surface, the disk drive must wait until the disk pack rotates around to the same location to attempt the operation again. The extra rotation results in a write or read inhibit that is treated as an error. These errors can affect the input/output speed of the individual disk drive and the system as a whole. If the problem is severe enough, the disk drive will be turned off or fenced due to its inability to read and write data. It is possible that the disk drive will be fenced due a system level mounting problem and not due to a problem with the disk drive itself. Corrective maintenance for shock and vibration induced errors will usually result in the replacement of a healthy disk drive.
Several approaches have been used in attempts to minimize the effects of self-induced vibrations, and externally induced shocks and vibrations on various disk drives. Many of these same approaches are also used with other moving-media type drives such as optical dives, magneto-optical drives, and tape drives, generically referred to as media drives.
A common shock and vibration damping approach is to attach each media drive to a system level drive tray through one or more springs. Springs provide a degree of mechanical isolation between neighboring media drives mounted in the drive tray, as well as isolation from externally induced shocks and vibrations. Springs, however, allow vibrational energy to remain in the media drive thus adding to the energy spectrum of the media drive environment. Springs also contact the media drive chassis in only a few specific locations that are selected based upon a center of mass and not based upon closeness to the vibration sources.
Resonant plates have also been incorporated in damping systems to control the frequency of vibrations present in the media drive""s chassis. The plates have a resonant frequency at which the media drive is relatively immune to vibration induced errors. Most of the vibrational energy present in the media drive""s chassis is converted to the resonant frequency by the plates. Plates by themselves, however, do not dissipate the vibrational energy. All of the energy that enters the plates eventually returns to the media drive chassis or is transferred away through the springs.
The present invention provides an improved damping mechanism and method of operation that addresses the limitations discussed above.
The present invention is a system for housing a media drive, a drive tray for housing the media drive, and a method of operation to attenuate shocks and vibrations for the media drive. The system includes a drive tray housing and one or more drive modules, each adapted to hold one media drive. One or more resilient layers are disposed between the drive tray housing and each drive module to attenuate shocks and vibrations for that drive module. In a preferred embodiment, at least two of the resilient layers are positioned on opposite sides of each drive module to prevent the drive modules from making hard contact with the drive tray housing. Each resilient layer has an associated cover layer that supports sliding of the drive modules with respect to the drive tray housing for insertion and removal purposes.
In the preferred embodiment, the resilient layers and cover layers are mounted inside one or more bays defined in the drive tray housing. Each bay being adapted to receive one drive module. In an alternative embodiment, the resilient layers and cover layers are attached to the individual drive modules.
Each drive module may contain one or more plates that engage the enclosed media drive. Each plate has a resonant frequency that is outside an adverse frequency range for the media drive. The plates convert vibrations entering or exiting the media drive into a resonant vibration at the resonant frequency of the plate.
One or more of the resilient layers may have a viscoelastic property for converting shocks and vibrations into heat. An adhesion layer may be placed between the resilient layers and the respective cover layers so that the cover layers constrain the adjoining surface of the resilient layers.
Accordingly, it is the object of the present invention to provide an improved mechanism and method of operation for attenuating shocks and vibrations for a media drive.
These and other objects, features, and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.